In accordance with the International Radio Regulations, all the existing radio communications are divided into more than 50 different services such as aeronautical communication, marine communication, terrestrial communication, satellite communication, broadcast, television, radio navigation, positioning and telemetering, remote control, space exploration and the like, each having a certain limited frequency band.
In the mobile communication service, all mobile phones have different communication frequency bands, for example, 890-960 MHz for GSM 900, 1710-1850 MHz for GSM1800, and 825-880 MHz for CDMA. In addition, the major operating frequency band for 3G is 1880-2025 MHz, while the frequency band for 4G granted by the Ministry of Industrial and Information Technology of PRC is such high frequency band as 2575-2635 MHz.
At present, there coexist 2G, 3G and 4G communication networks. Regardless of base stations or indoor distribution systems, each communication system is provided with its respective antenna. The existing antennas are narrow in band width; therefore, it is necessary to employ a plurality of antennas different in band width for satisfying the band widths of all 2G, 3G and 4G antennas, thus resulting in high station establishment costs. Multipath fading generally exits in receiving of a linearly-polarized antenna from another linearly-polarized antenna such that radio signals may severely fade at a certain moment. In order to solve this problem, the present base station and terminal antennas all are directed to polarization diversity receiving. That is, dual-channel dual-polarized antennas are employed.